1. Field of the Invention
The present invention relates to a closure device suitable for transcatheter operations, i.e., operations for closing and repairing intracardiac or vascular defects.
2. Description of Background Art
In general, shunt affections due to congenital cardiac anomalies have been treated by surgical operations. Such surgical treatments consequently require not only the treatment of the affected area but also thoracotomy that imposes a burden on the patient. In particular, the surgical treatment is a great burden to a child patient. For this reason, there has recently been developed a noninvasive procedure in which the intracardiac defect is repaired with a cardiac catheter adapted to be inserted transvascularly into a cardiac cavity.
For example, patent ductus arteriosus (PDA) that is one of shunt affections, has been treated so far by transvascularly inserting a closure device into a blood vessel with a catheter and then leaving it in the blood vessel to obstruct the blood flow passing therethrough. In this method, the patent ductus arteriosus is closed by introducing a spongy polyvinyl alcohol closure device, which is previously formed into a shape corresponding to the size and morphology of the arterial duct, into the diseased site to be treated through the femoral artery. Porstman reported the first clinical success of this method in 1967. On the other hand, Rashkind proposed a method of closing a patent ductus arteriosus with a closure device composed of united double umbrella-like members and adapted to be introduced into the diseased site through a femoral vein by a catheter.
However, the Porstman""s method is complex in operation and includes a high risk of injuring vessels since it is required to insert a closure device with a larger size than the arterial duct through the femoral artery, thus making it difficult to apply it to infant patients. On the other hand, the Rashkind""s method involves a problem such that the residual shunts appear frequently.
As a solution of the above problem, Japanese Patent unexamined publication No. 07-308331 discloses a tool for obstructing intracorporeal tubular cavity that consists of a shape-memory alloy provided with a ring at both ends and is recoverable into a conical coil shape toward the central part of the coil at a predetermined temperature around the body temperature. This tool is adapted to obstruct a shunt site by introducing it into the shunt site and allowing a thrombus to adhere to the coil portion, and thus it has a problem such that a leakage takes place frequently.
On the other hand, as a clinical closure device, straight coils have been put to practical use currently. However, the straight coil has the problem that the leakage occurs frequently as is the case with the shape-memory alloy coil. In addition, it has a trouble in fixing it on a morbid part and tends to cause total dislocation or dislodgement.
The present invention has been developed in view of the above circumstances and aims at providing a closure device for transcatheter operations, which is applicable to defects with any form at a low risk of injury of blood vessels and free from leakage and residual shunts.
The present inventors dedicated efforts to solution of the above problems and achieved the present invention on the basis of an idea of combining an easily-foldable flat closure member with a shape-restoring force and a longitudinally elasticated fixing member with a shape-restoring force.
According to the present invention, there is provided a closure device for transcatheter operations, comprising:
a longitudinally elasticated fixing member having a shape-restoring force, the fixing member having a relatively large-sized circular portion at both ends thereof, at least one of the circular portions being fixed in a ring and connected to the opposite circular portion by means of a connecting portion, said connecting portion being extended from the fixed circular portion and progressively decreased in size toward the opposite circular portion; and a closure membrane attached to said fixed circular portion for closing a defect.
In this case, the opposite or second circular portion may be fixed in a ring as well as the first circular portion. When the second circular portion is not fixed in a ring and thus has a free end, the second circular portion is provided at the free end thereof with a holding portion. The holding portion is generally formed into a small-sized ring. Further, the second circular portion is generally formed so as to have the same diameter as the first circular portion. If the second circular portion is fixed in a ring, the ring may be closed up with a closure membrane as well as the first circular portion.
As a closure membrane for closing the ring, it is preferred to use a fabric or non-woven fabric of a biocompatible material. The fixing member is preferably made of a wire of a superelastic metal or a shape-memory alloy with a transformation temperature ranging from 30 to 36xc2x0 C. and formed into a coil or zigzag.
Further scope of applicability of the present invention will become apparent form the detailed description given hereinafter. However, it should be understood that the detailed description and specific example, while indicating preferred embodiments of the invention, are given by way of illustration only; since various changes and modifications within the spirit an scope of the invention will become apparent to those skilled in the art form the detailed description.